Chevrolet Opala

The Chevrolet Opala was a mid-size car sold by General Motors do Brasil from 1969 to 1992. It was derived from the German Opel Rekord Series C and Opel Commodore Series A, but used USA-sourced engines, two four-cylinder engines: the Chevrolet 153 4-cylinder from Chevy II/Nova which later got a new crankshaft and cylinders changing its size to 151 (usually mistaken for the Pontiac Iron Duke engine), and the six-cylinder 250 from the contemporary line of North American car/light truck production. GM manufactured about one million units including the Opala sedan, Opala Coupé, and the station wagon variation, the Opala Caravan. It was replaced by the Chevrolet Omega in 1992, also an Opel spinoff. It was the first passenger car built by GM in Brazil, they previously only built light trucks.

It was used by the Brazilian Police for many years. The military dictatorship issued Opalas to its agents through the 1970s. Its reliability and easy maintenance made the Opala the choice of many taxi drivers and was also popular on racetracks.

The Opalas 250 cubic inch engine (4.1 L) was used in its replacement, the Chevrolet Omega (which made use of Electronic Fuel Injection in the GLS and CD trims) from 1995 to 1998. Some of the Opalas components and chassis were used in other Brazilian cars such as the Santa Matilde, Puma GTB, and the Fera XK (a Jaguar XK replica).

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Founded in January 1925, General Motors do Brasil only assembled (and later, manufactured) light trucks and utilities until the mid-1960s, when they decided to produce their first Brazilian car.

The options oscillated between the large American cars from the traditional car line, such as the Impala, and the lighter and economical models from German subsidiary Opel (Kadett, Olympia, Rekord and Commodore) that were imported to Brazil in small quantities. After hesitating between the small Kadett and the large Rekord/Commodore line, GMB opted for the latter, but later introduced the Kadett as well.

On November 23, 1966, in a Press Conference at the Club Atlético Paulistano in São Paulo, GM announced Project 676, the future Chevrolet Opala.

The name Opala comes from a precious stone, colourless when extracted from the soil, but which acquires multiple tones when exposed to light. Some commented that the name was a portmanteau of Opel and Impala, as the model was derived from the German Opel Rekord, and one of its engines (the 230 in³, and later, 250 in³ straight-six) came from the North American Chevrolet Impala. GM claims that this was not their intention, as the name Opala - one of six finalists from thousands of suggestions - was chosen by a journalist. Its rapid acceptance with the general public led to the approval of the choice.

At the opening of the sixth São Paulo Auto Show, on November 23, 1968, the Opala appeared on a rotating stage on a 16,140 square feet (1,499 m2) stand. Around the novelty there were several spectacles, including an appearance by Stirling Moss. Several Opala models were shown every half hour.

Chevrolet Opala coupé

The first model was the four-door sedan in the trims "Especial" (Special) and "Luxo" (Deluxe). Its attractive lines used curvy lines from the windscreen to rear fender, a shape that was referred to as "Coke Bottle styling", already in use at the time on the 1967 Chevrolet Camaro and Pontiac Firebird and the 1968 Chevrolet Corvette, but hints of the upcoming style were already clear on the 1965 Chevrolet Impala fastback coupé. A hardtop coupe was also offered with a silhouette resembling the first-generation Camaro/Firebird. The round headlamps (not squared, as in the Opel Rekord and Commodore), egg-crate grille, styling cues borrowed from the 1968 Chevy II Nova, and lamps fitted below the front bumper separated the Opala from its European Opel siblings. In the back, a chrome strip with "Chevrolet" in black was included with the more expensive trim. Small rectangular taillights (similar to those on America's 1967 Chevelle) were mounted on the tip of the rear overhang, and small reverse lights were mounted in the rear bumper, just below the fuel tank cap. An "Opala" badge (spelled in a similar font to the American Chevrolet Impala badge) was fitted on the rear fenders, and the engine badges (2500 or 3800) next to the front doors. Chrome hubcaps complemented the whitewall tires.

Both versions came standard with front bench seats (bucket seats weren't available early in production, but were later introduced) and column shifter. Reverse lights, fuel tank lock, and rear valance chrome strip were available only on the "Luxo" trim level.

In the fall of 1970, a more luxurious version was added called Comodoro, reflecting Europe's Opel Commodore. The Comodoro-4 received a somewhat more powerful version of the 2.5 liter four in some model years, with 88 PS (65 kW) rather than 80 PS (59 kW). The same engine was used in the Opala SS-4.[1] Even more luxurious was the Diplomata, which appeared in November 1979.[1]

Under the hood, which hinged backwards, the Opala originally offered two engine choices: the straight-four 153 cu in (2,507 cc) and the straight-six 230 cu in (3,764 cc). They were a very traditional design, with cast iron cylinder block and head, overhead valves, pushrods and steel pressed rocker arms, whose spherical fulcrum was GM's proprietary design. Fuel was fed from either single or double barrel carburetors. In 1973 the four was replaced by Pontiac's 151 cu in (2,474 cc) "Iron Duke" engine. The 3.8 had already been replaced by the bigger 4.1 (4,093 cc or 250 cu in) in 1971.

The Opala's engines had been already used for years in the USA: the 153 had emerged in the 1962 Chevrolet Nova, becoming the first inline four in a Chevrolet since 1928, and the 230 appeared in the 1963 Impala. The 151 cu in Pontiac Iron Duke was also found in AMC's Jeeps and Eagles, and was known for its versatility and toughness. Known for its reliability, the 153 was an industry benchmark until the 1980s. The straight-six later served as a stationary engine, a school bus engine, and even found its way into forklifts.

Facelifted four-door Opala, rear view

The larger engine crankshaft bearings had seven supports (five in four-cylinders) and the generous (if not redundant) size of its inner moving parts attributed to its durability and exceptional smoothness. The hydraulic valve lifters made for easy maintenance.

The straight-six's biggest limitation through the years was poor distribution of air-fuel mixture to the cylinders. Number one and six received the poorest ratio, with a higher percentage of air in the mixture, while the central ones tended to get a richer mixture, unbalancing the engine's stoichiometric efficiency. This design flaw could easily be solved by installing a race intake manifold that sported two or three two-barrel carburetors, as in stock car racing. Only in 1994, with the multipoint injection found in the Omega, was the engine's problem finally solved.

The performance of Opala 3.8L was actually quite pleasing; with a top speed of 112.5 mph (181.1 km/h) and acceleration from 0 to 60 mph (97 km/h) in about 11 seconds, it was the fastest Brazilian car of its time, losing the title the following year to the Dodge Dart whose 318 cu in V8 had all that the straight-six was missing. The two 2.5L fours did not offer as much vigor, but had enough torque enough for everyday use. The main complaint with the four-cylinder engines was their roughness - so rough that GM employees of the time called the engine "little Toyota", in allusion to the diesel engine installed in the locally built Toyota Bandeirante.

Both the Especial and Luxo had a manual gearbox, rear wheel drive, front independent suspension and rear live axle, both with helical springs. In front, the suspension components were anchored to one side, set in the unibody with screws, later known as the subframe. The tires were the first tubeless tires used on a car manufactured in Brazil. It had a diaphragmatic (or "Chinese hat") clutch spring, which was becoming popular throughout the world. The sporty Opala SS, originally only available with the "250" engine, was the first version to receive a four-speed manual gearbox. This was coupled with a tachometer and lots of matte black striping.[2]

When endurance races resumed in Brazil in 1973, the Opala found a great competitor, the Ford Maverick, which was powered by an engine with a displacement almost a full liter larger. It took Bob Sharp and Jan Balder, who placed second in the "24 Hours of Interlagos" in August of that year with an Opala, to convince GM do Brasil to field a more powerful engine.

By coincidence, engine development manager Roberto B. Beccardi was already working on an engine hop-up project on his own, but GMB wasn't interested in it until Sharp and Balder's loss.

Thus, in July 1974, GMB introduced the 250-S engine as an option for the Opala 4100. It was slightly different from the version that would be launched two years later: it didn't have a vibration dampener and the cooling fan came from the standard 2500, with four blades instead of six.

The Opala was now much faster than the Maverick GT, and Ford did not waste time. It quickly homologated a version of the Maverick with a four-barrel carburetor. On the racetrack, the determining factor for victory was the driver's skill and the pit crew's organization. The rivals walked side by side.